Already accustomed to winning on the mat, transgender teen wrestler Mack Beggs can now enjoy another victory -- a change in policy that will allow him to compete in some matches against boys, the gender with which he identifes.

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The organization that governs amateur wrestling in the United States recently changed its policy to allow transgender wrestlers to compete against the gender which they declare as their own.

Thanks to the new rule by USA Wrestling, Beggs, a 17-year-old junior at Trinity High School in Euless who is transitioning to male, can compete against boys in offseason, non-school events.

But in school competitions, Beggs will still have to wrestle girls -- a fact that has made him a target of criticism.

The student won the Texas state girls' title in wrestling last month, capping off a season in which he was undefeated -- but one that drew controversy.

Beggs has not yet completed his transition to male and he is undergoing doctor-prescribed testosterone treatments. Critics had questioned whether these treatments gave him an unfair advantage over girls, and one parent filed a lawsuit against the state's school-athletics governing body in an attempt to block Beggs from competing in the girls’ division when he is a senior next year.

After winning his 110-pound weight class in the state tournament, Beggs told ESPN he would prefer to compete against boys but that the University Interscholastic League, which oversees athletics in Texas's public primary and secondary schools, requires him to wrestle under the gender listed on his birth certificate.

“Because I’m a guy. It just makes more sense [to wrestle boys],” Beggs told ESPN. “Boys' wrestling is hard. It's really, really hard. But I'll do it. If it means wrestling with the guys, I'll do it.”

Beggs added that he's been "holding back" on testosterone treatments, taking lower doses, so as to be fair when wrestling girls.

"I don't want to cheat," he told ESPN. "That's not something I do. I don't cheat."

The University Interscholastic League allows Beggs to compete against girls even though he is taking testosterone. But the organization has a rule, which it says was approved through a referendum of its member school superintendents, that a student athlete's gender is based on his or her birth certificate.

The University Interscholastic League also notes on its website that under Texas law, people can go to court to change the gender on their birth certificate.

"The [league] strives to provide fair and equitable competitions for all students" and follows "a transparent process to make the rules that govern" competitions, the organization says on its website.

In contrast to the state organization's policy, USA Wrestling's has adopted the new policy that says wrestlers who transition before puberty shall be regarded as the gender with which they identify. The policy was adopted at the organization's executive meeting March 14.

The athlete need only have “declared that his gender identity is male” or that “her gender identity is female,” the new policy policy states.

Tony Black, USA Wrestling’s director of state services, told ABC News affiliate WFAA that the new policy is in line with International Olympic Committee guidelines adopted last year that remove all surgical requirements for transgender athletes to compete in Olympics and other international events concordant with their gender identity.

Black told WFAA that USA Wrestling's policy change grew out of “a changing culture and ensuring that we’re in line with the International Olympic Committee recommendations on this exact matter.”

Beggs told ESPN in his interview earlier this month that he has been taunted with slurs and boos during competitions. Some people “just automatically want to call me a cheater,” he said.

The teen said Texas' school athletic policymakers should “change the laws and then watch me wrestle the boys.”

"I mean, I've been winning before, when I didn't have testosterone," he told ESPN. "But now that, you know, I'm actually winning winning, people want to go crazy."